lunchbox::SpinLock Class Reference

A fast lock for uncontended memory access. More...

#include <spinLock.h>

Inheritance diagram for lunchbox::SpinLock:

Collaboration diagram for lunchbox::SpinLock:

Public Member Functions
LUNCHBOX_API	SpinLock ()
	Construct a new lock. More...
LUNCHBOX_API	~SpinLock ()
	Destruct the lock. More...
LUNCHBOX_API void	set ()
	Acquire the lock exclusively. More...
LUNCHBOX_API void	unset ()
	Release an exclusive lock. More...
LUNCHBOX_API bool	trySet ()
	Attempt to acquire the lock exclusively. More...
LUNCHBOX_API void	setRead ()
	Acquire the lock shared with other readers. More...
LUNCHBOX_API void	unsetRead ()
	Release a shared read lock. More...
LUNCHBOX_API bool	trySetRead ()
	Attempt to acquire the lock shared with other readers. More...
LUNCHBOX_API bool	isSet ()
	Test if the lock is set. More...
LUNCHBOX_API bool	isSetWrite ()
	Test if the lock is set exclusively. More...
LUNCHBOX_API bool	isSetRead ()
	Test if the lock is set shared. More...

Detailed Description

A fast lock for uncontended memory access.

If Thread::yield() does not work, priority inversion is possible. If used as a read-write lock, readers or writers will starve on high contention.

See also

ScopedMutex

Example:

/* Copyright (c) 2006-2014, Stefan Eilemann <eile@equalizergraphics.com>
 *
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License version 2.1 as published
 * by the Free Software Foundation.
 *
 * This library is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
 * details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#define TEST_RUNTIME 600 // seconds, needed for NighlyMemoryCheck
#include "test.h"

#include <lunchbox/atomic.h>
#include <lunchbox/clock.h>
#include <lunchbox/debug.h>
#include <lunchbox/init.h>
#include <lunchbox/lock.h>
#include <lunchbox/omp.h>
#include <lunchbox/spinLock.h>
#include <lunchbox/timedLock.h>

#include <iostream>

#define MAXTHREADS 256
#define TIME       500  // ms

lunchbox::Clock _clock;
bool _running = false;

template< class T > class Thread : public lunchbox::Thread
{
public:
    Thread() : lock( 0 ), ops( 0 ) {}

    T* lock;
    size_t ops;

    virtual void run()
    {
        ops = 0;
        while( LB_LIKELY( _running ))
        {
            lock->set();
#ifndef _MSC_VER
            TEST( lock->isSet( ));
#endif
            lock->unset();
            ++ops;
        }
    }
};

template< class T > void _test()
{
    T* lock = new T;
    lock->set();

#ifdef LUNCHBOX_USE_OPENMP
    const size_t nThreads = LB_MIN( lunchbox::OMP::getNThreads() * 3,
                                    MAXTHREADS );
#else
    const size_t nThreads = 16;
#endif

    Thread< T > threads[MAXTHREADS];
    for( size_t i = 1; i <= nThreads; i = i << 1 )
    {
        _running = true;
        for( size_t j = 0; j < i; ++j )
        {
            threads[j].lock = lock;
            TEST( threads[j].start( ));
        }
        lunchbox::sleep( 10 ); // let threads initialize

        _clock.reset();
        lock->unset();
        lunchbox::sleep( TIME ); // let threads run
        _running = false;

        for( size_t j = 0; j < i; ++j )
            TEST( threads[j].join( ));
        const float time = _clock.getTimef();

        TEST( !lock->isSet( ));
        lock->set();

        size_t ops = 0;
        for( size_t j = 0; j < nThreads; ++j )
            ops += threads[j].ops;

        std::cout << std::setw(20) << lunchbox::className( lock ) << ", "
                  << std::setw(12) << /*set, test, unset*/ 3 * ops / time
                  << ", " << std::setw(3) << i << std::endl;
    }

    delete lock;
}

int main( int argc, char **argv )
{
    TEST( lunchbox::init( argc, argv ));

    std::cout << "               Class,       ops/ms, threads" << std::endl;
    _test< lunchbox::SpinLock >();
    std::cout << std::endl;

    _test< lunchbox::Lock >();
    std::cout << std::endl;

    _test< lunchbox::TimedLock >();
    TEST( lunchbox::exit( ));

    return EXIT_SUCCESS;
}

Definition at line 38 of file spinLock.h.

Constructor & Destructor Documentation

LUNCHBOX_API lunchbox::SpinLock::SpinLock

(

)

Construct a new lock.

Version

1.0

LUNCHBOX_API lunchbox::SpinLock::~SpinLock

(

)

Destruct the lock.

Version

1.0

Member Function Documentation

LUNCHBOX_API bool lunchbox::SpinLock::isSet

(

)

Test if the lock is set.

Returns

true if the lock is set, false if it is not set.

Version

1.0

LUNCHBOX_API bool lunchbox::SpinLock::isSetRead

(

)

Test if the lock is set shared.

Returns

true if the lock is set, false if it is not set.

Version

1.1.2

LUNCHBOX_API bool lunchbox::SpinLock::isSetWrite

(

)

Test if the lock is set exclusively.

Returns

true if the lock is set, false if it is not set.

Version

1.1.2

LUNCHBOX_API void lunchbox::SpinLock::set

(

)

Acquire the lock exclusively.

Version

1.0

LUNCHBOX_API void lunchbox::SpinLock::setRead

(

)

Acquire the lock shared with other readers.

Version

1.1.2

LUNCHBOX_API bool lunchbox::SpinLock::trySet

(

)

Attempt to acquire the lock exclusively.

Returns

true if the lock was set, false if it was not set.

Version

1.0

LUNCHBOX_API bool lunchbox::SpinLock::trySetRead

(

)

Attempt to acquire the lock shared with other readers.

Returns

true if the lock was set, false if it was not set.

Version

1.1.2

LUNCHBOX_API void lunchbox::SpinLock::unset

(

)

Release an exclusive lock.

Version

1.0

LUNCHBOX_API void lunchbox::SpinLock::unsetRead

(

)

Release a shared read lock.

Version

1.1.2

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The documentation for this class was generated from the following file:

• spinLock.h